1. Field of the Invention
This invention relates to a Pulsed Plasma Thruster (“PPT”) and a method for making a PPT.
2. Related Art
As satellites become smaller and as larger satellites require highly precise motion control, a need arises for smaller thrusters. PPTs have been proposed for use in these kinds of applications and many different PPT designs have been attempted.
Spanjers (U.S. Pat. No. 6,269,629) discloses a micro-PPT that uses a coaxial cable configuration. Spanjers uses the insulation of the cable or the spacer, made of a copolymer, disposed between a cylindrical outer conductor and an inner conductor as the fuel.
Spanjers (U.S. Pat. No. 6,153,976) discloses a PPT that replaces a spark igniter with a mechanical switch that contacts the face of an electrically conductive propellant. This reference also provides a background description of PPT's in general.
Burton et al. (U.S. Pat. No. 4,821,509) discloses a pulsed electrothermal thruster. This invention attempts to provide conditions that lead to electrothermally-dominated flow. Specifically, a high pressure discharge with very low ionization is disclosed. The electrical discharge includes the use of a capillary tube, but the size of the capillary is governed by the need to produce high discharge pressures.
Burton (U.S. Pat. No. 5,425,231) discloses a gas fed pulsed electric thruster. This invention is gas fed and operates at an enormously high repetition rate. This is done in order to maximize the utilization of the gas propellant. In this design, the gas propellant is constantly flowing through the device rather than shutting the gas on and off between discharges.
LaRocca (U.S. Pat. No. 3,575,003) teaches a thruster that operates by accerating gasses. LaRocca discloses a device that includes an array of radially oriented electrodes. LaRocca also discloses the use of a specially formulated melted propellant that moves by the action of surface tension. This design does not provide the capability to operate a thruster using common liquid or melted solid substances as propellants.
While the related art generally teaches different PPT designs, none of the references teach a compact or micro-PPT that is susceptible to easy and rapid manufacture, includes no moving parts and is easy to deploy and integrate into existing and future satellite architecture. Current designs employ springs or other mechanical devices that are used to convey or advance a solid fuel bar. These springs or other mechanical devices can be very difficult or impractical to use on very small scales.